Data carrier having a chip including means for the controllable voltage supply to a further component of the data carrier
The invention in the first place relates to a data carrier as defined in the opening part of claim 1.
The invention in the second place relates to a chip as defined in the opening part of claim 8.
Such a data carrier and such a chip are known from the patent document U.S. Pat. No. 5,777,903 A. The known data carrier is a smart card, which is adapted to store data. The known data carrier has a chip which takes the form of a single-chip microcontroller and which includes a processor unit and additional memory means, such as a RAM, ROM and EEPROM. The chip has a supply voltage input, which is connected to a power supply and which forms the supply voltage circuit point, from which a supply voltage can be taken. The known data carrier includes two off-chip components, namely a display component and a keyboard component, which each have a separate supply voltage input connected to the output of the power supply interface. The connection between the output of the power supply interface and the supply voltage inputs of the chip and of the two further components is made with the aid of an external connection lead. Such external connection leads form a security risk because during the processing of data by means of the chip, i.e. by means of the processor unit included in the chip, current and voltage variations occur in the area of these connections, which enable an undesired access to the processed data, which is particularly critical when security-related data are processed. In this respect reference is for example made to known methods, such as a static power attack or a dynamic power attack.
It is an object of the invention to preclude the problems described hereinbefore and to provide an improved chip, so as to avoid the problems with the prior-art data carrier in a simple manner and by simple means.
According to the invention, in order to achieve the aforementioned object with a data carrier as defined in the opening part of claim 1, the characteristic features defined in the characterizing part of claim 1 are provided.
Furthermore, according to the invention, in order to achieve the aforementioned object with a chip as defined in the opening part of claim 8, the characteristic features defined in the characterizing part of claim 8 are provided.
As a result of the provision of the measures in accordance with the invention it is assured in a simple manner that the supply voltage output of the chip and, consequently, the external connection lead which is connected to this supply voltage output and which leads to the supply voltage input of a further component, can be brought at a potential value which during the processing of data with the aid of the on-chip data processing means inhibits an undesired access to the data being processed.
In a data carrier in accordance with the invention the potential control means may be formed, for example, by voltage divider means or voltage multiplier means. However, it has proved to be very advantageous when such a data carrier in addition has the characteristic features defined in claim 2. With the aid of such isolation means a particularly reliable manner of defining a desired potential value at the supply voltage output of the chip is achieved.
In a data carrier in accordance with the invention having isolation means as potential control means it has proved to be advantageous when in addition the characteristic features defined in claim 3 are provided. Thus, it is achieved in an advantageous manner that the isolation means have a highly autonomous design which does not affect the data processing. Moreover, this has the advantage that control by means of a digital signal can be effected simply and that the signal levels of the controlling digital signals and the signal levels of the signals to be controlled can be selected comparatively independently of one another.
It has proved to be very advantageous when a data carrier in accordance with as described in the preceding paragraph in addition has the characteristic features defined in claim 4, because this enables the supply voltage output of the chip to be brought simply at two fixed potential values or at a floating potential value.
The isolation switch means may utilize bipolar transistors. However, it has proved to be particularly advantageous if the isolation switch means are realized by means of field-effect transistors because this enables a power dissipation which occurs during operation of the chip to be minimized.
Furthermore, it has proved to be particularly advantageous if the potential value at the supply voltage output of the chip can be controlled by means of the field-effect transistors.
With a data carrier in accordance with the invention there are various possibilities for the generation of the control signal for the potential control means, which suitably take the form of isolation means. In this respect it has proved to be advantageous when a data carrier in accordance with the invention in addition has the characteristic features defined in claim 5, or claim 6, or claim 7, respectively. In a data carrier as defined in claim 5 the setting of the supply voltage output is simply program-controlled and is consequently highly flexible. A data carrier as defined in claim 6 advantageously guarantees that the supply voltage output of the chip is automatically set to a desired potential value during processing of data with the aid of the data processing means, which is particularly important for the processing of security-related data. A data carrier as defined in claim 7 advantageously guarantees that a desired security potential is produced at the supply voltage output of the chip when the memory means are accessed, for example to read or to write data. This is particularly important when security-related data are stored or read out.
The advantages described hereinbefore with reference to the data carriers defined in the claims 2 to 7 basically apply likewise to the chips defined in claims 9 to 14.
The above-mentioned as well as further aspects of the invention will become apparent from the embodiment described hereinafter by way of example and will be elucidated with reference to this example.